Process for manufacturing a plastic fuel tank

ABSTRACT

Process for manufacturing a plastic fuel tank equipped with an internal line by molding a parison using a mold comprising two cavities and a core, comprising the following steps: introducing the parison into the mold cavities; introducing the core inside the parison, said core having first been fitted with the line; closing the mold so that the cavities come into leaktight contact with the core; pressing the parison against the cavities by blowing through the core and/or applying a vacuum behind the cavities; fastening the line to the parison over at least two points using a device attached to the core; opening the mold to withdraw the core; and carrying out the final molding of the parison by blow molding and/or thermoforming, in which the line comprises, between its fastening points, a free length that is capable of coming into contact with the parison and/or with an accessory found thereon when the mold is closed, and wherein during the fastening step, at least one intermediate fastening point is created using a device attached to the core.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application under 35U.S.C.§371 of International Application No. PCT/EP2008/062510 filed Sep.1, 2008, which claims priority to French Patent Application No. 07.57991filed Oct. 2, 2007, these applications being incorporated herein byreference in their entirety for all purposes.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process for manufacturing a plasticfuel tank (FT).

BACKGROUND OF THE INVENTION

Fuel tanks on board vehicles of various kinds generally have to meetleaktightness and permeability standards in relation to the type of usefor which they are designed and the environmental requirements that theyhave to satisfy. At the present time, both in Europe and throughout theworld, there is a substantial tightening of the requirements regardingthe limitation of pollutant emissions into the atmosphere and into theenvironment in general.

To limit these emissions, care is taken in particular to position thecomponents (ventilation lines, valves, baffles, stiffeners, etc.) insidethe tank and/or the fill pipe (see in particular application WO2004/024487 in the name of the Applicant). However, when thesecomponents are fastened to the tank after it has been molded, it isgenerally necessary to make at least one opening in the tank so as to beable to introduce said components into the tank and to fasten themthereto. Hence there may be potential leakage problems near thisopening.

Several years ago the Applicant therefore developed a process ofinitially molding a cut parison (cut into two sections) in order to beable to introduce thereinto and fasten thereto components during theactual molding of the tank and to thus avoid drilling openings (seePatent EP 1 110 697 in the name of the Applicant).

This process has since been the subject of several improvementstargeting particular means for fastening these components: see inparticular Applications WO 2006/008308 (fastening of components by rivetpunching), WO 2006/095024 (fastening of ventilation lines that have apart that can be deformed due to the presence of a bend that isstretched during the attachment of these lines to the parison) and WO2007/000454 (fastening of components according to an ideal layout and inparticular, as regards the ventilation lines, while avoiding theformation of siphons).

These improvements have been able to be made due to the use of a corei.e. a part of suitable size and shape for being able to be insertedbetween the cavities of the mold when the parison is located therein andto fasten thereto the components inside the tank without the edges ofthe parison being welded (since the core must be removed before thefinal molding of the tank, a step during which the welding of theparison sections is carried out). Such a part (core) is, for example,described in Patent GB 1 410 215, the content of which is for thispurpose incorporated by reference into the present application.

However, during the implementation of these various improvements, theApplicant noticed that in certain cases the components were not in themolded and cooled tank, at the location at which the core had placedthem on the parison. The Applicant has also observed in certain cases(for example, in the case of saddle tanks, in the restriction leadingfrom one pocket to the other), a local degradation of the internalsurface of the wall of the tank which, although not visible from theoutside, may lead to a degradation of the FT performances as regards theimpermeability.

After analyses of the various cases observed, the Applicant has finallyfound the source of the problem: in general, the lines (ventilationlines, fuel or electricity supply lines, etc.) are only fastened to theFT by their ends and/or by their active points (for example; by theventilation valves in the case of ventilation lines) and they cantherefore, when the mold is being closed for the definitive molding ofthe tank (after having removed therefrom the core which has fastened thecomponents to the parison), come to press on the part of the parisonopposite and/or close to them.

It should specifically be noted that in order to be able to compensatefor the thermal expansions of the tank when in service, these lines aregenerally fastened loosely and may therefore make loops or have freelengths between their fastening points. In conventional FT manufacturingprocesses, where the lines are fastened to the molded and cooled tank,the presence of such loops is common and is not an obstruction.Conversely, in a process such as that described above where the linesare fastened when the parison is molten, these loops are in fact thecause of the aforementioned problem since they can rub against theparison (and weaken it) and/or against another accessory found therein(and move the latter relative to its ideal location).

SUMMARY OF THE INVENTION

The objective of the invention is therefore to provide a process thatmakes it possible to integrate a line into a plastic fuel tank when itis being manufactured by molding without damaging the internal wall oraltering the position of the other internal components.

For this purpose, the invention relates to a process for manufacturing aplastic fuel tank equipped with an internal line by molding a parisonusing a mold comprising two cavities and a core, said process comprisingthe following steps:

-   1. the parison is introduced into the mold cavities;-   2. the core is introduced inside the parison, said core having first    been fitted with the line;-   3. the mold is closed so that the cavities come into leaktight    contact with the core;-   4. the parison is pressed against the cavities by blowing through    the core and/or applying a vacuum behind the cavities;-   5. the line is fastened to the parison over at least two points    using a device attached to the core;-   6. the mold is opened to withdraw the core; and-   7. the final molding of the parison is carried out by blow molding    (by injecting a pressurized fluid inside the parison) and/or    thermoforming (by applying a vacuum behind the cavities),    in which the line comprises, between its fastening points, a free    length that is capable of coming into contact with the parison    and/or with an accessory found thereon when the mold is closed, and    according to which, during step (5), at least one intermediate    fastening point is created using a device attached to the core.

It should be noted that in this process, steps 1 and 2 may take placesimultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIG. 1 illustrates a cross section through a high-density polyethylene(HDPE) clip (1), inserted into which are ventilation lines (2) andelectrical lines (3) and which is intended to fasten these lines to amolten HDPE parison;

FIG. 2 illustrates the fastening of a ventilation line (2) to a parison(4) using a moveable device (5) actuated by a jack (not illustrated)using a relief in the mold cavities;

FIG. 3 illustrates a similar fastening method as in FIG. 2 but where themold cavities are equipped with two oblique jacks (7);

FIG. 4 illustrates an enlarged view of a clip (1) made from HDPE,provided with a single wide opening (12) inserted into which are anelectrical line (3), a fuel supply line (4) and a fuel return line (4′);

a clip that incorporates another variant of the present invention;

FIG. 5 illustrates another enlarged view of a clip (1) made from HDPEand provided with a single wide opening (12) inserted into which are anelectrical line (3), a fuel supply line (4) and a fuel return line (4′);and

FIG. 6 illustrates yet another enlarged view of a clip (1) made fromHDPE and provided with a single wide opening (12) but without showinglines inserted therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The expression “fuel tank” is understood to mean an impermeable tank,able to store fuel under diverse and varied usage and environmentalconditions. An example of this tank is that with which motor vehiclesare fitted.

The fuel tank according to the invention is made of plastic.

The term “plastic” means any material comprising at least one syntheticresin polymer.

Any type of plastic may be suitable. Particularly suitable plasticsbelong to the category of thermoplastics.

The term “thermoplastic” is understood to mean any thermoplasticpolymer, including thermoplastic elastomers, and also blends thereof.The term “polymer” is understood to mean both homopolymers andcopolymers (especially binary or ternary copolymers). Examples of suchcopolymers are, in a non-limiting manner: random copolymers, linearblock copolymers, other block copolymers and graft copolymers.

Any type of thermoplastic polymer or copolymer, the melting point ofwhich is below the decomposition temperature, is suitable. Syntheticthermoplastics having a melting range spread over at least 10 degreesCelsius are particularly suitable. Examples of such materials includethose that exhibit polydispersion in their molecular weight.

In particular, it is possible to use polyolefins, thermoplasticpolyesters, polyketones, polyamides and copolymers thereof. A blend ofpolymers or copolymers may also be used; similarly it is also possibleto use a blend of polymeric materials with inorganic, organic and/ornatural fillers such as, for example but in a non-limiting manner:carbon, salts and other inorganic derivatives, natural or polymericfibres. It is also possible to use multilayer structures composed ofstacked and joined layers comprising at least one of the polymers orcopolymers described above.

One polymer that is often used is polyethylene. Excellent results havebeen obtained with high-density polyethylene (HDPE).

The wall of the tank may be composed of a single thermoplastic layer, orof two layers. One or more other possible additional layers may,advantageously, be composed of layers made of a barrier material toliquids and/or gases. Preferably, the nature and thickness of thebarrier layer are chosen so as to minimize the permeability of liquidsand gases in contact with the internal surface of the tank. Preferably,this layer is based on a barrier resin, that is to say a resin that isimpermeable to the fuel such as, for example, EVOH (a partiallyhydrolysed ethylene/vinyl acetate copolymer). Alternatively, the tankmay be subjected to a surface treatment (fluorination or sulfonation)for the purpose of making it impermeable to the fuel.

The tank according to the invention preferably comprises an EVOH-basedbarrier layer located between the HDPE-based outer layers.

According to the invention, the tank is produced by molding a parison.The term “parison” is understood to mean a preform, which is generallyextruded and is intended to form the wall of the tank after molding tothe required shapes and dimensions. This preform does not necessarilyhave to be a one-piece preform.

Thus, advantageously, the parison is in fact made up of two separatepieces, which may be two sheets, for example. However, these piecespreferably result from cutting one and the same extruded tubular parisonas described in the aforementioned Application EP 1 110 697, the contentof which for this purpose is incorporated by reference in the presentapplication. According to this variant, once a single parison has beenextruded, this parison is cut over its entire length, along twodiametrically opposed lines, to obtain two separate parts (sheets).

By comparison with the molding of two separately extruded sheets, thethickness of which is constant, this approach makes it possible to useparisons of varying thickness (that is to say in which the thickness isnot constant over their length), obtained using a suitable extrusiondevice (generally an extruder equipped with a die and a punch, theposition of which is adjustable). Such a parison takes account of thereduction in thickness that occurs during molding at certain points onthe parison, as a result of non-constant rates of deformation of thematerial in the mould.

After a parison has been molded in two pieces, these pieces generallyform the lower and upper walls respectively of the fuel tank, eachhaving an inner surface (pointing towards the inside of the tank) and anouter surface (pointing towards the outside of the tank).

The mold used in the process according to the invention comprises a coreas defined previously and two cavities that are intended to be incontact with the outer surface of the parison, the parison being moldedby blow molding (pressing the parison against these cavities using apressurized gas injected into the parison) and/or thermoforming (drawinga vacuum behind the mold cavities).

Preferably, it takes place by blow moulding, but preferably while alsoproviding suction (drawing a vacuum) behind the cavities to keep theparison in the mold when the latter is not closed and pressurized.Hence, it preferably comprises a degassing step prior to step (6).Generally, in order to do this the parison is first pierced (for exampleby puncturing it with a needle) and then the fluid is discharged fromthe mold (for example using a valve).

In the process according to the invention, the line is fastened to theinner surface of the parison by virtue of a device attached to the corethat generally comprises a jack. Preferably, the core allows severalaccessories to be fastened to the inside of the tank, these accessoriespreferably being preassembled on the core, before it is inserted intothe mould, at their corresponding location on the parison (see theaforementioned Application WO 2007/000454).

According to one particularly advantageous variant of the invention, theline and at least one other component inside the tank are first mountedon a common support (frame) that is used for loading the core. Thus,even before loading into the core, the components may be positioned andassembled on this frame which allows excellent repeatability in the X,Y, Z positioning of the components and facilitates the handling ofassemblies that are sometimes complex and therefore not very ergonomic(a ventilation system, for example). The frame may be handled by anoperator or by a robot, depending on the weight of the parts inquestion. As regards the loading of the core, it is in fact carried outby fastening the frame directly to the core, with the componentsarranged opposite devices that will fasten them to the parison and thatare attached to the core (clamps actuated by jacks, for example). Thisapproach makes it possible to make savings in terms of the cycle timesince the assembly of the various components to the support can becarried out independently of the molding process.

It should be noted that the use of a frame for loading the core is alsoadvantageous outside the context of the invention for any process formolding an FT with fastening of internal components by means of thecore.

The core used in the process according to the invention may also be usedfor blowing the pressurized gas required for blow molding of the parisonand, when the parison to be blow-moulded is in 2 sections, the core mayalso be used to keep the edges of these two sections hot, during steps(3) to (5) at least of the process.

Finally, the core may also be used at least partially for processcontrol. For this purpose, it is possible for example to incorporate acamera into the core so as to display and check the quality of thefastening of the pipe (and of other possible components of the tank) byimage analysis. One or more sensor(s) for measuring a quantity orquantities such as force, travel, pressure and temperature may also befitted onto the core so as to better control the fastening of the pipeto the parison.

The present invention is particularly suitable for fastening an internalline to two points of a same parison part and in particular to the innersurface of the upper (wall) part of the tank (whether or not the latteris molded from a parison in two separate pieces). These points aregenerally separated by a few cm, or even by more than ten centimetres.

The term “line” is understood within the context of the invention tomean a pipe, i.e. a duct of elongated shape, preferably open at its endsand of substantially tubular cross section. The line according to theinvention may be a ventilation line, a line for pumping fuel, forreturning fuel from the engine to the tank (in the case of dieselengines), or for filling; an electric line (in this case, the pipe isgenerally the sheathing of an electrical cable), etc. This line ispreferably used to transport something (a fluid, electricity, etc.).According to the invention, it is fastened to the tank (or moreprecisely: to the parison, the word “tank” denoting the finished, moldedarticle) at least two points, generally via its ends and/or activepoints.

The term “fastened” is understood to mean that the line is eitherdirectly in contact with the wall of the tank, or attached to anintermediate fastening means that is, itself, directly in contact withthe tank wall. The term “contact” is understood to mean either amechanical fastening (that can be dismantled) or a weld (or molecularinterpenetration). The latter gives good results from the point of viewof permeability and is practical to use within the context of theinvention, as the parison is melted/softened during moulding. Therefore,other techniques (preferably also taking advantage of the fact that theparison is melted/softened) can also be used such as, for example, rivetpunching. This is a technique described in Application FR 04/08196 inthe name of the Applicant, and the content of which is incorporated byreference in the present application.

Preferably, the line is attached by an intermediate fastening means andmost particularly preferably the latter has a geometry such that theline can slide into it easily (i.e. with little friction) and thereforehave a relative mobility so as to ensure that it can move withoutconstraint especially in the major axis of the shrinkage of the tankwhich occurs after molding (during cooling of said tank). For thispurpose, a clip (i.e. a ring or part (slice) of a cylinder having alength less than its diameter) gives good results and in particular aclip having a diameter such that the line, when it is inserted thereinand hangs by gravity, is only in contact with one part of its innersurface. One way of achieving this in practice consists in ensuring thatthe line (or lines, where appropriate) occupies at most ¾ of theinternal volume of the clip, preferably at most ⅔ and most particularlypreferably at most half of the available internal volume.

The expression “active points” is understood to mean a part or anaccessory of the line fulfilling an active role in the tank, i.e. forexample: a ventilation valve; a connection (coupling) to an accessoryoutside the tank (for example, an electrical connection with a voltagesource; a hydraulic connection to an engine, etc.). According to oneparticularly advantageous variant of the invention, at least onefastening point of the line is formed from an accessory that makes itpossible, due to the fact that it is fastened to the parison and due tothe manner in which it is attached to the line, to prevent this linefrom rotating. This is because said line may, in certain cases, comprise“free” accessories (that are attached to the line but are not fastenedin the tank), of which the rotation (driven by that of the line) couldalso damage the parison. One way of achieving this in practice consistsin providing the line and the accessory with complementary reliefs thatfit together by a quick coupling and which prevent the relative rotationof these components. A “fir-tree” fitting with rotational stop isparticularly suitable for this purpose.

It should be noted that use of an anti-rotation fastening is alsoadvantageous outside the scope of the invention, when it is a questionof fastening a line inside an FT.

The line according to the invention may be made from any materialsuitable for its function. In the case of a pipe that transports a fluidat a temperature close to ambient (such as a ventilation pipe for thetank (the purpose of which is generally to connect the top of the tankto a device for adsorbing fuel vapours or a canister), a vapour-ventingline (that sends some of the vapours to the top of the fill pipe whenthe tank is being filled), a line for fixing the maximum fuel level (theobstruction of which by the level of fuel causes the nozzle to trip),etc.), this pipe is generally based on a plastic, and in particular onHDPE.

Preferably, as described in the aforementioned Application WO2006/095024, the line can be deformed between the points for fasteningit to the tank due to the presence of at least one bend. The expression“can be deformed” is understood to mean that the distance between thetwo fastening points of the pipe is variable. The term “bend” isunderstood in fact to denote any deformation that allows the pipe to belengthened when stretched (such as a coil (convolution), or one or morecorrugations (bellows, crimping) for example). One variant which is verysuitable in practice (because it is easy to apply by a simple(preferably hot) deformation of the pipe) consists in making at leastone bend shaped like an “S”, a wave or a “V” (or more strictly a “W” ifthe ends of the bend are counted) in the required region. Thus, in away, a spring is made in the pipe, which is stretched when the pipe ismounted onto the parison in a manner (or to an extent) such that it ispreferably at rest (or almost at rest) when the molded tank is cooled.

Preferably, the line of the process according to the invention is aventilation pipe that comprises at least one valve. Preferably, it ischaracterized by the presence of a valve at least one of its ends andparticularly advantageously, it comprises a valve at each of its ends,and it is via these valves that the pipe is fastened to the tank, andalso by an intermediate fastening point that has no other role than toeliminate the loop (free length).

This is because in tanks comprising several (at least two) pockets(saddle tanks), it is generally advisable to ventilate at least one(some) of them. One means for achieving this that is suitable inpractice consists in equipping the pocket or pockets that it is desiredto ventilate with a ventilation valve and to connect this valve to acanister via a pipe as described previously and also by a valve attachedbetween the pipe and the canister. Such a valve may fulfil severalfunctions: prevent liquid fuel from entering into the canister in thecase of a wave or if the vehicle rolls over (ROV or Roll Over Valvefunction); prevent overfilling (ISR function); trap drops of liquid fuelthat may be entrained by the vapour (liquid-vapour separation function),etc. The present invention is particularly suitable in the context offastening ventilation pipes that join together various valves on a fueltank.

In the case of a saddle tank as described previously, a criticallocation already mentioned above is constituted by the central part ofthe tank that joins the pockets together and that generally has areduced height. The present invention especially makes it possible toavoid damaging the wall of the tank at this location, where theventilation line or lines must pass even though the dimensions arereduced, by providing an additional fastening point in or close to thisregion.

More generally, the invention makes it possible to overcome the damagingof the parison and/or displacement of its internal accessories due tothe presence of loops (free lengths) in the internal lines byeliminating said loops via making an intermediate fastening pointbetween the ends of these loops, this point generally having no otherfunction than that of removing the loops.

When the line is based on the same material as the inner surface of theFT (generally HDPE), this intermediate fastening may be created bywelding simply by pushing the free loop against said surface using adevice attached to the core (which generally comprises a jack for thispurpose, for example a hydraulic jack). However, in particular when itis a question of a ventilation line, said line may collapse (flatten)considering the high temperature of the parison.

Therefore, as already mentioned above, according to one advantageousvariant of the invention, the intermediate fastening point is createdusing a fastening part which received the line prior to its fasteninginside the tank and which will be effectively welded to the parison atthe intermediate fastening point by pressure using a device attached tothe core. Preferably, this is a part made from HDPE so that it can bewelded to the FT by pressing against its wall. A simple HDPE clip, whichreceives the line at the required location, is particularly suitable forthis purpose.

According to another advantageous variant, the line is at least in theregion of the intermediate fastening point, partially based on amaterial that has a greater thermal resistance than that of the tank(for example: based on PA (polyamide) or on POM (polyoxymethylene) whenthe tank is made from HDPE) and the mold cavities comprise, at thelocation of said fastening point, a suitable relief in order to ensurethat under the pressure of a device attached to the core the line lodgesitself in said relief at this location, one section of the parison thenbeing clamped between said relief and the line. This relief must thenhave a geometry such that, when the tank is demoulded, the pipe isfastened by said clamped section. The relief in the cavities isgenerally in the shape of a groove. Advantageously, this groove issurrounded by at least two oblique jacks that locally push the parisonfrom the outside (i.e. from the cavities towards the core) so that itmarries up with the line at the intermediate fastening location.

In this variant, either the entire line may be based on a materialhaving an improved thermal resistance such as PA or POM or, preferably,the line is made from HDPE but is equipped with a sheath based on such amaterial at the location of its intermediate fastening point.

Two preferred variants of the invention (respectively with clips or witha relief in the mold cavities) are respectively illustratedschematically by FIGS. 1 and 2-3. A clip that incorporates several otherpreferred variants of the invention is illustrated in FIGS. 4 to 6.

In these figures identical numbers denote identical or similarcomponents.

FIG. 1 shows a cross section through an HDPE clip (1), inserted intowhich are ventilation lines (2) and electrical lines (3) and which isintended to fasten these lines to a molten HDPE parison. This clip isloosely fastened to (receives) a “free” loop of these lines and it willbe welded to the parison using a jack present on the core that will pushthe clip onto/into the parison in order to weld it thereto, all this,therefore, without deforming the lines. This clip is provided with twowide openings into which the lines are inserted very loosely so as toensure that they can move without constraint especially during theshrinkage of the tank after molding. It also comprises welding platforms(weld feet) or excrescences on its surface that is intended to be weldedto the wall of the tank (lower surface).

FIG. 2 shows the fastening of a ventilation line (2) to a parison (4)using a moveable device (5) actuated by a jack attached to the core(these are not illustrated) and which, by displacement (indicated by thearrow) and pressure on the line, makes it possible to lodge this line ina groove (6) present in the mold cavities (only one part of which, nextto the groove, is represented). It can be seen therein how the parison(4) surrounds the line (2) when it is in the molten state. Oncesolidified, it will keep the line (2) in place in a relief correspondingto that of the groove (6).

FIG. 3 illustrates a similar fastening method but where this time themold cavities are equipped with two oblique jacks (7) that contribute(through their displacement in the direction of the arrows) to correctcovering of the line (2) by the parison (4) level with the groove (6).

In FIGS. 2 and 3, dimensions are given by way of example.

FIGS. 4 to 6 are enlarged views of a clip (1), also made from HDPE,provided with a single wide opening (12) that has an indicated height of10 to 20 mm, inserted into which are (in FIGS. 4 and 5, as FIG. 6illustrates the clip alone) an electrical line (3), a fuel supply line(3′) and a fuel return line (4′).

These lines are held by a clamping collar (10) inserted into an openingmade in a tongue (9) molded as one part with the clip (1).

This collar makes it possible to keep the cables and lines against oneanother, in particular for easier handling during loading of the core.It is also possible to avoid the risk of jamming in the clip (whichwould negate its purpose) through a random arrangement of cables andlines in this same clip during blow moulding.

The clip illustrated in these figures comprises a base (11) that enablesit to be welded to the wall of an HDPE tank, and also a casing (8) thatmay be used to house a part (for example, an electrical connector)during the molding process, which it is then possible to dislodge afterdemolding in order to fasten it where it should be fastened inside thetank.

This electrical connector may be used to connect the component havingthis connector to an electrical component mounted during the final(manual) assembling operations. Without this casing (8), the operatorwould have to look for the connector in the tank.

A metal ring (12) is integrated into the welding base (11) so as to beable to easily locate the clip from the outside when the tank is molded.

It is worth noting that the idea of providing a plastic part with ametal insert also gives this same advantage outside the scope of thepresent invention, namely: in the frame of a process for controlling thelocation of internal plastic accessories in a plastic FT. It is namelyso that this metal insert (which may be of any shape, for instance ametal disk) makes it easier to locate the part using a metal detector,X-rays scanning etc. . . . Hence, in the case of a plastic vent valve(like a ROV or Roll Over Valve; an FLVV or Fill Limiting Vent Valve, . .. ), a metal disk can be inserted between the cover and the body of thevalve (in the case of two parts valves), in a recess on top of the coverbefore mounting the valve inside the tank etc. . . .

1. A process for manufacturing a plastic fuel tank equipped with aninternal line by molding a parison using a mold including two cavitiesand a core, said process comprising the following steps:
 1. introducingthe parison into the mold cavities;
 2. introducing the core inside theparison, said core having first been fitted with the line;
 3. closingthe mold so that the cavities come into leaktight contact with the core;4. pressing the parison against the cavities by blowing through the coreand/or applying a vacuum behind the cavities;
 5. fastening the line tothe parison over at least two points using a device attached to thecore;
 6. opening the mold to withdraw the core; and
 7. carrying outfinal molding of the parison by blow molding and/or thermoforming,wherein the line includes, between fastening points thereof, a freelength that is capable of coming into contact with the parison and/orwith an accessory found thereon when the mold is closed, wherein, duringstep (5), at least one intermediate fastening point is created using thedevice attached to the core, and wherein the line is attached by a cliphaving a diameter such that, when the line is inserted therein and hangsby gravity, the line is only in contact with one part of an innersurface of the clip.
 2. The process according to claim 1, wherein theparison includes two separate pieces originating from a singularextruded tubular parison that is cut over an entire length thereof,along two diametrically opposed lines.
 3. The process according to claim1, wherein the line and at least one other component inside the tank arefirst mounted on a common support that is used for loading the core. 4.The process according to claim 1, wherein at least one fastening pointof the line is formed from an accessory that prevents the line fromrotating, and wherein the accessory is fastened to the parison and theaccessory is attached to the line.
 5. The process according to claim 1,wherein the line is a ventilation pipe that has a valve at each endthereof, and wherein the ventilation pipe is fastened to the tank viathe valves and by an intermediate fastening point.
 6. The processaccording to claim 5, wherein the tank is a saddle tank including acentral part of reduced height that joins together at least two pocketsthat each include one of the valves, and wherein the intermediatefastening point is in or close to the central part.
 7. The processaccording to claim 1, wherein the at least one intermediate fasteningpoint is created using the intermediate fastening part that receives theline before said line is fastened inside the tank, said intermediatefastening part being welded to the parison at the at least oneintermediate fastening point by pressure using the device attached tothe core.
 8. The process according to claim 7, wherein the intermediatefastening part is a high-density polyethylene (HDPE) clip.
 9. Theprocess according to claim 7, wherein the line is at least in a vicinityof the at least one intermediate fastening point, partially based on amaterial that has a greater thermal resistance than a thermal resistanceof the tank, and wherein the mold cavities comprise, at said at leastone intermediate fastening point, a relief in order to ensure that undera pressure of the device attached to the core, the line is lodged insaid relief, one section of the parison then being clamped between saidrelief and the line.
 10. The process according to claim 9, wherein therelief in the cavities is a permanent groove-shaped relief or is aretractable relief including two oblique jacks that locally push theparison from an outside thereof so that said relief marries up with theline at the at least one intermediate fastening point.
 11. The processaccording to claim 1, further comprising attaching a tongue of theintermediate fastening part to a collar surrounding the line.
 12. Theprocess according to claim 1, wherein the line occupies at most ¾ of aninternal volume of the clip.